Process for the production of sodium bisulfite.



EHOElfiSWILLIAMSTAINER nurcnrns, LUKE HARG-REAVES, AND ALFRED (ii-marine nurmrneanivr, or MInnLnWrcH, ENGLAND.

PROCESS FOR THE PRGDUCTION OF SODIUM BISULFITE.

liquidform in an economical and eliic'ien nianr "r. v

Tl invention consists in so disposing, as hereinafter more particularly. defined,, a mass or masses of hyd ated carbonate ora ixture of-hydrated carbonates or of the anhydrous and hydrated carbonates of sodium, that upon the passage of"'gaseous sulfur dioxid thereinto, carbon dioxid is progressively generated, which proceeding through the said mass or masses n advance of the sulfur'dioxld, converts the carbonates into a form in which they are more readilyacted upon by the sulfur dioxid for production of the bisulfite.

The invention further consists in the em- 1 ployment in the process above indicated, of equimolecular proportions of the carbonates and their combinediwater so as to obtain the bisulfite in a solid form. 3

The invention further consists inthe em ployment in the process above indicated of a carbonate or carbonates having such proportions of combined water that yater is see free during the. reaction and gives a con centrated bisulfite solution.

The invention further consists in employing hydrates, hydrated carbonates or a mixture of anhydrous and hydrated carbonates of the alkali or alkaline earth metals for a preliminary purification treat ment of the gases generated or resulting from the combustion of sulfur in. theatmosphere for the production of the required sulfur dioxid, so that oxygen and sulfur trioxid are eliminated and sulfur dioxid and nitrogen (together with carbon (llOXJLl if a carbonate {be used) pass forward from the. purifier for utilization in the above/ 11 1" dicated proce rss', the sulfur dioxid (and if I the Specification of Letters Patent.

of Middleuicb,

bisulfite may be produced in either solid or- Patented reuse; rare.

Application filedAugust 16, 1916. Serial No. 115,302. v

mass or masses of the material, in the inanpresent the carbon dioxid) actingiup'on the nor indicated, and the nitrogen and resultvessels charged with a powdered mixture of soda crystals and soda ash and cause dry sulfur dioxid gas to pass therethrough.

It is essential that the mass shall be so disposed that the entering gas cannot act upon the Whole or practically-the Whole thereof and so convert it directly into sodium bisulfite but that a relatively small area shall be exposed to such gas and the distance through the mass be of considerable length wherel'iy the double reaction before specified and hereinafter more particularly referred to, results. I

The quantities of soda ash and soda crystals are so adjusted, are regard "being bad to the degree of purity of the soda ash, that the carbonate and Water are present inequiniolecular proportions. The action of the sulfur dioxid at the commencement of the process results in the generation of carbon dioxid according to the formula:

in" ooncineaut o ensio QQNaHSUfidOCO The carbon dioxid in its turn now'acts upon the portion of the: mixture not'y'et acted upon by the sulfur dioxd converting same into bicarbonate of soda according to the following formula 1 QOlY aHCO Nuiconso zuuusoh -co It will be seen that in accoiwflance with our process, except at the commencement of the rcactionwhen the sulfur CllOXlCl acts directly upon the mixture of carbonates the reaction accomplished in. tu'ostages; the

first sta e bein that in which the mixture g l L v .r is converted lnto bicarbonate by carbon d1- 11o oxid and the second that in which the bicarbonate is converted by the sulfur dioxid into bisulfite with liberation of carbon di- OXl(l.

Anyone or more of the towers or reaction vessels may be disconnected for discharging and charging purposes without interfering with the progress of the process in the remaining towers or vessels.

Instead of employing a mixture of soda crystals and soda ash as aforesaid, we

anay employ the mono-hydrated earbonate (Ba CO ILO) :the reactions are, however,

to react with anhydrous sodium carbonate,

which is preferably in the form of soda ash, the reaction being represented its-follows:-

anansog na oo =2Na so,+oo,+H,o It will of course be understood that the dry solid body may be used for preparing a hot saturated sulfite solution, from which the crystalline salt will separate on cooling without previous evaporation.

If it is desired to obtain concentrated bi- Y sulfite liquor by our improved bis'ulfite proc mation of the bicarbonate of soda.

level. modification of our bisulfite process are theess, ,We employ sodafcrystals '(Na CO 10H O) only in the towers or reaction vesselsso that water is liberated during 'the for- Such water trickles downthe towers or vessels and dissolves the bisulfite formed at a lower The reactions accompanying this same as those hereinbefore described namely, the generation of carbon dioxid by theaction of the sulfur dioxid onthe soda crystals, the conversion of soda crystals to sodium bicarbonate by the carbon dioxid, with however, the liberation of water, and the pro duction of bisulfite from the bicarbonate by the action of sulfur. dioxid. By feeding the soda crystals into the tops of the towers and drawing olf the bisulfite liquor,}the' process can be carried on continuously. -The liquor produced is a concentrated bisulfite solution.

In. order to minimize the amount of impurity in the finished product, we provide ,for a preliminary purification of the sulfur dioxid before it'is employed in the bisulfite producing process so that any oxygen and sulfur trioxid which may be produced during the combustion of sulfur in the atmosphere for the productlon of the sulfur dioxid, may be effectually eliminated. For

this purification treatment, we employ a The sulfurterial into bisulfite which is then oxidiz'ed' by any free oxygen and also by the sulfur trioxid present, with the production of.bi-

sulfate and the liberation of sulfur dioxid,

The latter, together with the nitrogen of the air in which the sulfur was burned, then passes to the ordinary reaction towers or vessels in which the bisulfite either insolid or liquid form is to be produced.

If the purifying tower be charged with a hydrated carbonate or amixture of anhydrous and hydrated carbonates, then there will issue from the tower sulfur dioxid, carbon dioXi-d and nitrogen (from the atmosphere). l The carbon dioxid and sulfur dioxid will then act on the material in the reaction towers or vessels.

By the aforesaid pi'i'rification process. we eliminatethe production of bisulfate in the ordinary reaction towers orvessels. The rate of generation and supply of the sulfur dioxid gas may be varied by varying the rate of supply of the air for combustion by a fan, pump or'other means.

From the last of the series of the reaction towers or vessels, a mixture of carbon dioxid and nitrogen issues, and we employ this to driveout Ithe sulfur dioxid occluded in the solid bisulfite product, transferring; each tower or-vessel, as the reactions therein are completed, to the end of the series of towers, this beingaccomplished by means of suitable valves: and connections or otherwise. The s'ulfur'dioxid driven oif 1n the aforesaid manner may be recovered and utilized .in the towers where the reactions are still proceeding.

During the reactions occurring in our improved process considerable heat is evolved: the cooling of the reaction tower may be taken as an indication that the reaction therein is completed.

.lVe desire it to be understood that we make no claim to the mere action of sulfur dioxid gas upon sodium carbonate for the direct production of sodium bisulfite, such reaction being well known and having been accomplished in various types of apparatus having for their object to insure a more intimate contact of the gas and solid by di-- vidiug the latter up into powder form and agitating it continuously in the presence of the gas. I In accordance with oiir invention. the efliciency of the action depends upon the eifect of the. carbon dionid liberated by the sulfur dioxid gas which gives the material into which it passes a very uniform porosity, so that the sulfur dioxid gas is readily absorbed, without the necessity for agitating the materials or crushingthem to powder.

Having now described our invention what we claim as new and desire to secure by Letters Patent is Y 1. The herein described process for the manufacture of sodium bisulfite consisting in subjecting a closely packed stationary charge of sodium carbonate, at least in part hydrated, to gaseous sulfur dioxid to convert a portion directlyv into bisulfite with the liberation of carbon dioxid; subjecting the remaining portion of the charge first to the action of the evolved carbon dioxid to con vert it into a bicarbon; e of marked porosity and then to the action of \sulfur dioxid to convert said bicarbonate into bisulfite .in the desired form, the evened-carbon dioxid proceeding through the charge in advance eration of carbon dioxid; subjecting the re maining portion of the charge first to the action of evolved carbon dioxid to convert it into a bi-carbo'nate of marked porosity and then to the action of sulfur dioxid to convert said bicarbonate into bisulfite in the desired form. r

3. lhe process for the manufacture-0f sodium bisulfite wherein sodium carbonate at least in part hydrated to provide equimolecular proportions of carbonate and ciombined water, islsubjected to the action of gaseous sulfur dioxid so'that after the initial direct conversion of a portion of the carbonate into bisulfite withthe liberation of carbon dioxidythe remaining portion of the carbonate is subjected to a double reaction consistingfof the conversionof the carbonatein'to bicarbonate by the previously liberated carbon dioxid and the subsequent conversion of the bicarbonate to bisulfite by the sulfurdioxid, the finished product having the nitrogen and carbon dioxid issuing from the treated materials passed therethrough to drive off any sulfur dioxid 0ccluded in the bisulfite, as set forth.

In testimony whereof we have signed our names to this Specification in the presence of two subscribing witnesses;

THOMAS WlLLIAM STAINER HU'I'OHINS. LUKE. HARGREAYES. ALFRED CHARLES DUNNINGHAM.

Witnesses:

An'rH n HUGHES, V HULDA HUG ES. 

